But GM's increase may not be the norm. Analysts predict that sales of new cars and light trucks in the U.S. rose slightly from a year earlier as few deals and economic worries kept car shoppers home.
Vice President of Sales Don Johnson says unemployment, low consumer confidence and uncertainty over the federal debt ceiling scared some buyers off.
GM sold 214,915 vehicles in July, including nearly 25,000 Cruzes. That could make it America's top-selling car for the second straight month.
Sales of the Chevrolet Equinox and GMC Terrain small crossovers rose 80 percent.
GM is among the first companies to report U.S. sales Tuesday.